Views: 0 Author: Site Editor Publish Time: 2026-05-13 Origin: Site
Hole collapse is one of the most common and dangerous sudden failures in the construction of rotary drilling rig pile foundations. It can lead to construction rework, project delays, buried drill rods, equipment damage, and even personnel safety accidents. Especially during the rainy season, soft soil geology, and complex geological construction, the risk of borehole collapse increases significantly, posing serious hidden dangers to the quality and construction safety of pile foundation engineering. This article combines practical experience on construction sites to deeply analyze the core reasons for the collapse of rotary drilling rigs, dismantle emergency response plans for different collapse scenarios, and supplement preventive measures to help construction personnel quickly handle and scientifically avoid, ensuring the smooth progress of pile foundation construction.
The collapse of a rotary drilling rig is not accidental, but rather stems from four major issues: geological conditions, construction operations, equipment configuration, and environmental factors. Most of the collapses are caused by the superposition of multiple factors. Only by accurately identifying the causes can targeted emergency plans be developed to avoid exacerbating the danger caused by improper handling.
Geological factors are the core innate causes of borehole collapse, especially during construction in special geological formations, where the probability of borehole collapse significantly increases. Geological conditions such as soft soil layers, sand layers, pebble layers, and weathered rock layers have poor soil or rock stability, and the borehole walls are prone to collapse due to loss of support during the drilling process; When the groundwater level is too high, water pressure will impact the borehole wall, causing soil softening and loss, leading to borehole collapse; If there are underground caves and cracks in the construction area, it is easy for the borehole wall to leak and collapse during the drilling process, and such collapses are often sudden and harmful, making it difficult to predict in advance.
Improper human operation is the most common cause of hole collapse in rotary drilling rigs, and most hole collapses can be avoided through standardized operations. The drilling speed is too fast, especially in soft soil and sand layers, and the hole wall does not form a stable structure in time, which is easily disturbed by the drill bit and collapses; The mud wall protection is not in place, and the mud density and viscosity do not meet the requirements, which cannot effectively wrap the hole wall and balance the water pressure inside the hole, resulting in water seepage and collapse of the hole wall; Frequent lifting, swinging, or excessive shaking of the drill rod during the drilling process can disturb the soil around the borehole wall and damage its stability; Failure to install steel cages and pour concrete in a timely manner after drilling, resulting in prolonged exposure of the borehole wall to air or water, and soil softening leading to borehole collapse.
The mismatch between the equipment configuration and working conditions of the rotary drilling rig will indirectly increase the risk of hole collapse. The drill rod material has insufficient strength and is not firmly connected, making it prone to shaking, displacement, and disturbance of the hole wall during drilling; Improper torque adjustment of the power head, too fast or too slow speed, either cannot effectively break the rock layer or excessively disturb the hole wall; The equipment legs are not firmly supported, the body is tilted, and the drilling rod is subjected to uneven force during drilling, which can cause the hole wall to be unbalanced and collapse; Insufficient power of the mud pump and poor circulation of mud prevent timely discharge of sediment from the hole. Accumulation of sediment can reduce the stability of the hole wall and induce hole collapse.
Changes in the external environment are also important factors that can trigger borehole collapse, especially the impact of severe weather and surrounding construction. During the rainy season, precipitation is concentrated, causing rainwater to wash away holes and infiltrate into them, resulting in saturated soil moisture content and decreased strength on the hole walls, which can easily lead to hole collapse; Rainstorm and gale weather will lead to the shaking of the drilling rig and the collapse of the orifice, aggravating the danger; Surrounding construction (such as excavation of foundation pits and heavy equipment compaction) will disturb the soil layer in the construction area, damage the stability of the borehole wall, and induce collapse of surrounding boreholes; Sudden rise and fall of groundwater level can cause a sharp change in water pressure within the borehole, which can impact the borehole wall and lead to borehole collapse.
After the collapse of the rotary drilling rig, do not blindly handle it. Follow the core principle of "controlling the danger first, then scientifically handling it, and finally restoring construction", prioritize the safety of personnel and equipment, and avoid expanding the scope of the collapse. Before disposal, all drilling operations should be stopped, unrelated personnel should be evacuated from the site, the stability of the drilling rig should be checked, and a warning area should be set up to prevent secondary collapse from causing casualties; Based on the degree and cause of the collapse, develop targeted disposal plans, and strictly prohibit blind drilling and forced drilling; After the disposal is completed, it is necessary to comprehensively check the stability of the hole wall, confirm that there are no hidden dangers, and then gradually resume construction.
According to the degree of collapse, it can be divided into three categories: mild collapse, moderate collapse, and severe collapse. The focus of disposal varies in different scenarios, and precise measures and scientific operations are required to avoid improper disposal that exacerbates the danger.
Minor collapse of the hole is manifested as a small amount of collapse at the orifice, a small amount of sediment inside the hole, no obvious cracks on the hole wall, and no risk of buried drilling. The core of disposal is to timely stop losses, reinforce hole walls, and clean up sediment. Firstly, stop drilling and slowly lift the drill rod to a safe position to avoid disturbing the collapsed hole area; Then adjust the mud proportion and viscosity, increase the mud circulation, use the mud to wrap the hole wall and discharge the sediment in the hole; After the mud circulation in the hole is stable and the sediment is cleaned up, slowly lower the drill rod and use low-speed, light pressure drilling method to gradually repair the hole wall. After confirming the stability of the hole wall, resume normal construction rhythm.
Moderate collapse of the borehole is characterized by local collapse of the borehole wall, significant sedimentation inside the borehole, increased borehole diameter, slight signs of buried drilling, and no sustained expansion of the collapse range. The core of disposal is to reinforce the hole wall, control the collapse range, clean up the sediment, and remove the drill rod. Stop drilling first, maintain mud circulation, and prevent further expansion of the collapsed hole; If the drill rod is not buried, slowly lift the drill rod and then add materials such as clay and bentonite into the hole to adjust the mud density and enhance the mud wall protection effect; After the hole wall stabilizes, use a slag bucket to clean the sediment inside the hole, and if necessary, use a small drilling rig to assist in cleaning; After the sediment cleaning is completed, the drill rod should be lowered again and the drilling should be carried out at low speed. The hole wall should be gradually repaired to ensure that there is no risk of collapse before resuming construction.
Severe collapse of the borehole is characterized by extensive collapse of the orifice, severe damage to the borehole wall, buried drilling rods, and significant loss of mud in the borehole. The scope of the collapse continues to expand, and there is a risk of equipment overturning and personnel injury. The core of disposal is emergency risk control, equipment evacuation, step-by-step cleaning, and re drilling. Firstly, immediately stop all operations, evacuate all personnel from the site, fix the position of the drilling rig, and prevent it from tipping over due to ground collapse; If the drill pipe is buried, do not forcefully lift it to avoid pipe breakage and equipment damage. High pressure grouting can be used to inject cement slurry into the hole to reinforce the hole wall and fix the drill pipe; After the hole wall is completely stable, use professional equipment to clean up the collapsed waste residue and gradually remove the buried drill rods; After the cleaning is completed, re survey the geological conditions, adjust the construction plan, replace the suitable drilling tools and mud parameters, and re drill the hole to ensure construction safety.
The core of dealing with the collapse of rotary drilling rigs is "prevention first, combined with prevention and control". Through pre control and avoidance of various triggering factors, the probability of collapse can be significantly reduced. Before construction, conduct a comprehensive survey of the geological conditions in the construction area, develop a special construction plan in advance for special strata such as soft soil and sand layers, and select suitable drilling tools and mud parameters; Standardize drilling operations, control drilling speed, avoid drilling too fast or too quickly, smoothly lift and release the drill during the drilling process, and reduce disturbance to the hole wall; Strengthen mud management, monitor mud density and viscosity in real-time, adjust and optimize in a timely manner, and ensure the effectiveness of mud wall protection; After drilling, accelerate the installation of steel cages and concrete pouring progress, and shorten the exposure time of the hole wall; During rainy season construction, it is important to protect the openings and promptly drain any accumulated water to prevent rainwater from washing away the openings; When there are construction activities in the surrounding area, take protective measures in advance to avoid soil disturbance.
During the emergency response process of borehole collapse, it is necessary to avoid common operational errors and prevent the escalation of the danger. It is strictly prohibited to blindly lift or forcefully drill after a hole collapse, in order to avoid drill pipe breakage, equipment damage, or secondary hole collapse; It is strictly prohibited to adjust the mud parameters arbitrarily. The mud density and viscosity should be scientifically adjusted according to geological conditions and collapse conditions; During the disposal process, a dedicated person should be arranged on site to command, maintain vigilance, and prohibit unrelated personnel from entering the work area; Operators must wear safety protective equipment in a standardized manner, strictly follow emergency plans, and avoid safety accidents caused by operational errors; After the disposal is completed, a comprehensive investigation of the stability of the hole wall and equipment status is required to confirm that there are no hidden dangers before resuming construction.
